Add ExecuteJavaScriptForTest and make all tests use it

android_webview/browser/aw_browser_main_parts.cc

Index: android_webview/browser/aw_browser_main_parts.cc
diff --git a/android_webview/browser/aw_browser_main_parts.cc b/android_webview/browser/aw_browser_main_parts.cc
index c312757c424302acad071e884018cdaa5f4187a3..8f203e51cc79d1aabc039f3035c49d67fa00167c 100644
--- a/android_webview/browser/aw_browser_main_parts.cc
+++ b/android_webview/browser/aw_browser_main_parts.cc
@@ -15,6 +15,7 @@
 #include "base/android/memory_pressure_listener_android.h"
 #include "base/files/file_path.h"
 #include "base/path_service.h"
+#include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_switches.h"
@@ -108,6 +109,8 @@ void AwBrowserMainParts::PreMainMessageLoopRun() {
 
   gfx::GLSurface::InitializeOneOff();
 
+  content::RenderFrameHost::AllowInjectingJavaScriptForAndroidWebView();
+
   // This is needed for WebView Classic backwards compatibility
   // See crbug.com/298495
   content::SetMaxURLChars(20 * 1024 * 1024);